Lithography system and method thereof

ABSTRACT

A method includes transferring a wafer over a wafer stage on a wafer table. The wafer table includes a table body, a wafer stage, a first sliding member, a second sliding member, a first cable, a first bracket and a second bracket, and a stopper. The second sliding member is movable along a first direction, in which the first sliding member is coupled to a track of the second sliding member, the first sliding member being movable along a second direction vertical to the first direction. The first bracket and the second bracket are connected by a leaf spring. The method includes moving the wafer stage toward the edge of the table body, such that the wafer stage pushes the first cable outwardly, such that the leaf spring is moved toward a first protective film on a surface of the stopper facing the leaf spring.

PRIORITY CLAIM AND CROSS-REFERENCE

The present application claims priority to U.S. Provisional ApplicationSer. No. 63/072,632, filed Aug. 31, 2020, which is herein incorporatedby reference.

BACKGROUND

The semiconductor integrated circuit (IC) industry has experiencedexponential growth. Technological advances in IC materials and designhave produced generations of ICs where each generation has smaller andmore complex circuits than the previous generation. In the course of ICevolution, functional density (i.e., the number of interconnecteddevices per chip area) has generally increased while geometry size(i.e., the smallest component (or line) that can be created using afabrication process) has decreased. This scaling down process generallyprovides benefits by increasing production efficiency and loweringassociated costs. Such scaling down has also increased the complexity ofIC processing and manufacturing. For these advances to be realized,similar developments in IC processing and manufacturing are needed. Forexample, the need to perform higher resolution lithography processesgrows. One lithography technique is extreme ultraviolet lithography(EUVL). Other techniques include X-Ray lithography, ion beam projectionlithography, electron beam projection lithography, and multiple electronbeam maskless lithography.

The EUVL employs scanners using light in the extreme ultraviolet (EUV)region, having a wavelength of about 1-100 nm. Some EUV scanners provide4× reduction projection printing, similar to some optical scanners,except that the EUV scanners use reflective rather than refractiveoptics, i.e., mirrors instead of lenses. EUV scanners provide desiredpatterns on wafers by transferring mask patterns defined by an absorberlayer. Currently, binary intensity masks (BIM) accompanied by on-axisillumination (ONI) are employed in EUVL. In order to achieve adequateaerial image contrast for future nodes, e.g., nodes with the minimumpitch of 32 nm and 22 nm, etc., several techniques, e.g., the attenuatedphase-shifting mask (AttPSM) and the alternating phase-shifting mask(AltPSM), have been developed to obtain resolution enhancement for EUVL.But each technique has its limitation needed to be overcome. Forexample, an absorption layer however may not fully absorb the incidentlight and a portion of the incident light is reflected from theabsorption layer. Also the thickness of the absorption layer causes theshadowing effect. All of these often result in reduced aerial imagecontrast, which may lead to poor pattern profiles and poor resolution,particularly as pattern features continue to decrease in size. It isdesired to have improvements in this area.

BRIEF DESCRIPTION OF THE DRAWINGS

Aspects of the present disclosure are best understood from the followingdetailed description when read with the accompanying figures. It isnoted that, in accordance with the standard practice in the industry,various features are not drawn to scale. In fact, the dimensions of thevarious features may be arbitrarily increased or reduced for clarity ofdiscussion.

FIG. 1 is a schematic view of lithography system in accordance with someembodiments of the present disclosure.

FIG. 2 is a schematic view of a lithography system in accordance withsome embodiments of the present disclosure.

FIG. 3 is a schematic view of load locks in accordance with someembodiments of the present disclosure.

FIGS. 4A and 4B are schematic views of gate valve assemblies inaccordance with some embodiments of the present disclosure.

FIG. 5 is a schematic view of a wafer table of a lithography chamber inaccordance with some embodiments of the present disclosure.

FIG. 6A is a schematic view of a wafer table of a lithography chamber inaccordance with some embodiments of the present disclosure.

FIG. 6B is a schematic view of a leaf spring of a wafer table of alithography chamber in accordance with some embodiments of the presentdisclosure.

FIGS. 6C and 6D are schematic views of a stopper of a wafer table of alithography chamber in accordance with some embodiments of the presentdisclosure.

FIGS. 7A and 7B are side views of a wafer table of a lithography chamberin accordance with some embodiments of the present disclosure.

FIG. 8 is a schematic view of a wafer table a lithography chamber inaccordance with some embodiments of the present disclosure.

FIGS. 9A and 9B are side views of wafer table of a lithography chamberin accordance with some embodiments of the present disclosure.

FIG. 10 illustrates a method of forming a semiconductor device inaccordance with some embodiments of the present disclosure.

FIG. 11 illustrates a method of forming a semiconductor device inaccordance with some embodiments of the present disclosure.

DETAILED DESCRIPTION

The following disclosure provides many different embodiments, orexamples, for implementing different features of the provided subjectmatter. Specific examples of components and arrangements are describedbelow to simplify the present disclosure. These are, of course, merelyexamples and are not intended to be limiting. For example, the formationof a first feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, the present disclosure may repeat reference numerals and/orletters in the various examples. This repetition is for the purpose ofsimplicity and clarity and does not in itself dictate a relationshipbetween the various embodiments and/or configurations discussed.

Further, spatially relative terms, such as “beneath,” “below,” “lower,”“above,” “upper” and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. The spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly.

FIG. 1 is a schematic view of lithography system in accordance with someembodiments of the present disclosure. The advanced lithography process,method, and materials described in the current disclosure can be used inmany applications, including fin-type field effect transistors(FinFETs). For example, the fins may be patterned to produce arelatively close spacing between features, for which the abovedisclosure is well suited. In addition, spacers used in forming fins ofFinFETs can be processed according to the above disclosure.

FIG. 1 is a schematic view of lithography system in accordance with someembodiments of the present disclosure. Shown there is a EUV lithographysystem 10. Although the EUV lithography system 10 is illustrated ashaving a certain configuration of components, it will be appreciatedthat the disclosed lithography system 10 may include additionalcomponents (e.g., additional mirrors) or having less components (e.g.,less mirrors).

The EUV lithography system 10 includes a EUV source vessel 110. A fueldroplet generator 120 is connected to the EUV source vessel 110 and isconfigured to generate a plurality of fuel droplets 112. In someembodiments, the fuel droplets 112 generated by the fuel dropletgenerator 120 are provided into the EUV source vessel 110. In someembodiments, the fuel droplets 112 may include tin (Sn). In otherembodiments, the fuel droplets 112 may include a different metalmaterial. In some embodiments, the EUV source vessel 110 can also bereferred to as a radiation source, in which radiation source employs alaser produced plasma (LPP) mechanism to generate plasma and furthergenerate EUV light from the plasma.

The EUV lithography system 10 may also include a droplet positiondetection system which may include a droplet imager 140 disposed in theEUV source vessel 110 that captures an image of one or more fueldroplets 112. The droplet imager 140 may provide this captured image toa droplet position detection feedback system (not shown), which can,e.g., generate a droplet position and trajectory in response to ananalysis result of the captured image. The position detection feedbacksystem can thus generate a droplet error in response to the generateddroplet position and trajectory, e.g., based on a droplet-by-dropletbasis, or on average. In some embodiments, the droplet imager 140 mayinclude a fine droplet steering camera (FDSC), a droplet formationcamera (DFC), and/or suitable devices.

The EUV lithography system 10 further includes a primary laser having alaser source 102 configured to produce a laser beam 104. In someembodiments, the laser source 102 may include a multi-stage laser havinga plurality of stages configured to amplify laser light produced by aprior stage. The laser beam 104 passes through a beam transport system106 configured to provide the laser beam to a focusing system 108. Thefocusing system 108 includes one or more lenses 108 a, 108 b and/ormirrors arranged within a beam line and configured to focus the laserbeam 104. The laser beam 104 is output from the focusing system 108 tothe EUV source vessel 110.

The laser beam 104 transmits through a collector mirror 118 locatedwithin the EUV source vessel 110. Then, the primary laser beam 104generated by the laser source 102 intersects the fuel droplets 112. Insome embodiments, the primary laser beam 104 may be a carbon dioxide(CO₂) laser. In other embodiments, the primary laser beam 104 mayinclude alternative types of lasers. When the primary laser beam 104strikes the fuel droplets 112, the primary laser beam 104 heats the fueldroplets 112 to a predetermined temperature. At the predeterminedtemperature, the fuel droplets 112 shed their electrons and become aplasma 114 including a plurality of ions. In some embodiments, the ionsemit EUV radiation 116 (e.g., having a wavelength of approximately 13.3nm to about 13.7 nm).

In some embodiments, the collector mirror 118 has a concave curvature.In some embodiments, the collector mirror 118 may include a multi-layercoating having alternating layers of different materials. For example,in some embodiments, the collector mirror 218 may include alternatinglayers of molybdenum and silicon configured to operate as a Braggreflector. The concave curvature of the collector mirror 218 focuses theEUV radiation 116 generated by the plasma 114 toward an intermediatefocus (IF) unit 130 within an exit aperture of the EUV source vessel110. The intermediate focus unit 130 is located between the EUV sourcevessel 110 and a scanner 200 including optical elements configured todirect the EUV radiation 116 to a workpiece (e.g., a semiconductorsubstrate). In some embodiments, the intermediate focus unit 130 mayinclude a cone shaped aperture configured to provide for separation ofpressures between the EUV source vessel 110 and the scanner 200. In someembodiments, the intermediate focus unit 130 may extend into the scanner200.

The EUV lithography system 10 may also include an EUV energy monitor 150disposed in the EUV source vessel 110. The EUV energy monitor 150 isdesigned to monitor the EUV intensity or energy generated from the EUVsource vessel 110. For example, the EUV energy monitor 150 includes anEUV sensing element, such as a diode, designed to be sensitive to theEUV light and configured to effectively detect the EUV light. In otherexamples, the EUV energy monitor 150 includes a plurality of diodesconfigured in an array to effectively detect the EUV light formonitoring purpose. In some embodiments, a dose error is calculatedbased on the sensed EUV intensity (or energy). For example, when thesensed EUV intensity (or energy) is below a predetermined thresholdvalue, such situation can be referred to as a dose error. Generally, thedose error is related to the plasma instability, through monitoring theEUV intensity by the EUV energy monitor 150, the dose error can beextracted from the monitored EUV intensity. Therefore, when a dose erroris occurred, it indicates that the plasma 114 is unstable.

In some embodiments, the EUV lithography system further includes adroplet collection element 125 disposed in the EUV source vessel 110 andlocated opposite to the droplet generator 120. The droplet collectionelement 125 is configured to collect fuel droplets 112 that are notvaporized during formation of the EUV radiation 116 and/or fragments offuel droplets 112 generated during formation of the EUV radiation 116.

The EUV radiation 116 output from the EUV source vessel 110 is providedto a condenser 210 by way of the intermediate focus unit 130. In someembodiments, the condenser 210 includes first and second surfaces 212 aand 212 b configured to focus the EUV radiation 116, and a reflector 214configured to reflect the EUV radiation 116 towards an EUV photomask220. The EUV photomask 220 is configured to reflect the EUV radiation116 to form a pattern on a surface of a semiconductor wafer 250. Toproduce the pattern, the EUV photomask 220 may include a plurality ofabsorptive features 222 a, 222 b, and 222 c arranged on a front surfaceof the EUV photomask 220. The plurality of absorptive features 222 a,222 b, and 222 c are configured to absorb the EUV radiation 116, suchthat the reflected rays of EUV radiation 116 conveys a patterned definedby the EUV photomask 220.

The EUV radiation 116 is filtered through reduction optics including aseries of first to fourth mirrors 230 a, 230 b, 230 c, and 230 d, whichserve as lenses to reduce a size of the pattern carried by the EUVradiation 116. In some embodiments, the fourth mirror 230 d conveys theEUV radiation 116 onto a on a layer of photoresist disposed on a surfaceof the semiconductor wafer 250. The EUV radiation 116 irradiatesparticular regions of the layer of photoresist based on the patterncarried by the EUV radiation 116, and thus the layer of irradiatedphotoresist layer can be patterned after developing it. Therefore,subsequent processing can be performed on selected regions of thesemiconductor wafer 250.

FIG. 2 is a schematic view of a lithography system 20 according to thepresent disclosure. The lithography system 20 may be applied to patternsemiconductor wafers, as discussed above with respect to thesemiconductor wafer 250 of FIG. 1. Here, the wafers 250 are indicated bydashed circles. Generally, the wafers are moved from a wafer handler260, through load locks 264, 264 and a wafer exchange chamber 266, to alithography chamber 271. It is understood that the lithography processdiscussed in FIG. 1 is performed when the wafer 250 is positioned in thelithography chamber 271. In some embodiments, prior to performing thelithography process, the wafers 250 in the wafer handler 260 may havebeen undergone several processes, such as resist-apply, pre-bake, andother processes . . . etc. After the lithography process, wafers arereturned to the wafer handler 260 for further processing steps, such asdevelopment, post bake, and the like.

The wafer handler 260 is separated from the load locks 264, 264 by gatevalve assemblies 262, 263. The load locks 264, 265 are separated fromthe wafer exchange chamber 266 by gate valve assemblies 267, 268.Accordingly, the load locks 264, 265 can also be referred to as chambersthat are separated from the wafer handler 260 and the wafer exchangechamber 266 by respective gate valve assemblies 267, 268. In someembodiments, the load locks 264, 265 may further be connected to vacuumand venting elements (not shown) that allow the load locks 264, 265 tobe transitioned from atmospheric pressure to vacuum (pumped-down) andback to atmospheric pressure again (vented). In this way, the waferexchange chamber 266 can be held at a high vacuum while wafer handler260 is held at atmospheric pressure. The load locks 264, 265 thus serveto move wafers in and out from the wafer exchange chamber 266 whiletransitioning from atmospheric pressure to high vacuum.

In some embodiments, the wafer exchange chamber 266 may include a robotarm 269. The robot arm 269 is used to transfer wafers from the loadlocks 264, 265 to the lithography chamber 271. In some embodiments, therobot arm 269 may include a single end-effector, or dual, non-robotic,transport mechanisms could also be used without departing from the scopeof the present disclosure.

The wafer exchange chamber 266 is connected to lithography chamber 271by a gate valve assembly 270. In some embodiments, the lithographychamber 271 includes wafer stages 272, 273. The wafer stages 272, 273are capable of movement in the directions indicated for fine alignmentand exposure processes. The lithography chamber 271 thus furtherincludes projection optics or other elements necessary to perform thelithography patterning. While lithography chamber 271 is illustrated tohave two wafer stages 272, 273, less or more wafer stages may also beemployed.

FIG. 3 is a schematic view of the load locks 264, 265 in accordance withsome embodiments of the present disclosure. As shown in FIG. 3, the loadlock 264 is coupled to the gate valve assembly 262, and the load lock265 is coupled to the gate valve assembly 263, respectively. Thefollowing discussions use the load lock 264 and gate valve assembly 262as example, while it is understood that the load lock 264 and gate valveassembly 263 may include similar or the same configuration, thusrelevant details will not be repeated for simplicity.

The gate valve assembly 262 includes a gate valve seat 310 and a gate330 facing the gate valve seat 310. In some embodiments, the gate valveseat 310 of the gate valve assembly 262 may be fixed on a surface of abody 2642 of the load lock 264. Furthermore, the gate valve seat 310 mayinclude an opening 312, and the opening 312 may be aligned with a sloton the body 2642 of the load lock 264, such that the opening 312 iscommunicated with a chamber 2643 in the body 2642 of the load lock 264,which allows the wafer (e.g., the wafer 250) passes in and out from thechamber 2643 of the load lock 264 through the gate valve assembly 262.

On the other hand, the gate 330 of the gate valve assembly 262 may bemovable along at least one direction. For example, the gate 330 may bemovable along the vertical direction, such that when the gate 330 ismoved upwardly, the gate 330 may press against the gate valve seat 310and seal the opening 312 of the gate valve seat 310, such that the loadlock 264 may be gaseously isolated from a space that is coupled toanother side of the gate valve assembly 262.

In some embodiments, the load lock 264 further includes a lid 2644 overthe chamber 2643 in the body 2642 of the load lock 264. The lid 2644 maycover the chamber 2643 of the load lock 264. In some embodiments, thelid 2644 may include a thermal shield (not shown).

FIGS. 4A and 4B are schematic views of gate valve assembly 262 of FIG. 3in accordance with some embodiments of the present disclosure. FIG. 4Aillustrates a condition where the gate 330 is separated from the gatevalve seat 310 to reveal the opening 312 of the gate valve seat 310.FIG. 4A illustrates a condition where the gate 330 presses against thegate valve seat 310 to seal the opening 312 of the gate valve seat 310.

In greater detail, the gate 330 includes a valve plate 332, and asealing material 334 conformally disposed on the top edge 3320 of thevalve plate 332. In some embodiments, the sealing material 334 may bemade from a flexible or elastic material, such as rubber. In someembodiments, the top edge 3320 of the valve plate 332 has a section3320A, and sections 3320B and 3320C on opposite sides of the section3320A. The section 3320A of the top edge 3320 extends along thehorizontal direction, and can be regarded as a horizontal surface. Onthe other hand, the sections 3320B and 3320C are inclined with respectto the section 3320A. As the sealing material 334 is conformallydisposed on the top edge 3320 of the valve plate 332, the sealingmaterial 334 is therefore may also include a horizontal portion andinclined portions on opposite sides of the horizontal portion.

With respect to the gate valve seat 310, the gate valve seat 310 has asurface 320 to which the sealing material 334 on the valve plate 332 ofthe gate 330 is pressed. In some embodiments, the surface 320 has asection 320A, and sections 320B and 320C on opposite sides of thesection 320A. The section 320A of the surface 320 extends along thehorizontal direction, and can be regarded as a horizontal surface. Onthe other hand, the sections 320B and 320C are inclined with respect tothe section 320A. In some embodiments, the gate valve seat 310 is madeof metal, and thus the surface 320 of the gate valve seat 310 is made ofmetal.

In some embodiments, a protective film 340 is conformally disposed onthe surface 320 of the gate valve seat 310. In some embodiments, theprotective film 340 substantially covers an entirety of the surface 320of the gate valve seat 310. That is, the protective film 340 may coverthe sections 320A, 320B, and 320C of the surface 320 of the gate valveseat 310. In some embodiments, the protective film 340 may be anadhesive film, which is detachable from the surface of the gate valveseat 310, and may be made of a material that is different from amaterial of surface 320 of the gate valve seat 310. In some embodiments,the protective film 340 may include a material having frictioncoefficient less than 0.3, and having a tensile strength (at breakpoint) greater than 48 Mpa in vacuum. In some embodiments, theprotective film 340 may be ultra high molecular weight polyethylene(UHMWPE) tape. In some other embodiments, the protective film 340 may besilicon pressure sensitive adhesive (PSA). In some embodiments, theprotective film 340 may satisfy a request in a Total Organic Carbon(TOC) test of outgassing limit for refractories is zero (or negligiblesmall) detected under temperatures about 40° C. and about 100° C., thisensure that the protective film 340 would not be decomposed under theselected temperatures, and would not contaminate other structures in thelithography chamber 400.

As shown in FIG. 4B, when the gate 330 is move upwardly, the sealingmaterial 334 on the valve plate 332 of the gate 330 presses theprotective film 340 on the surface 320 of the gate valve seat 310. Thesealing material 334 may be squeezed against the protective film 340 onthe surface 320 of the gate valve seat 310, so as to seal gas thatpasses through an opening 312 of the valve seat 310. In someembodiments, as the protective film 340 substantially covers an entiretyof the surface 320 of the gate valve seat 310, the sealing material 334does not directly contacts the surface 320 of the gate valve seat 310when the gate 330 is move upwardly and seal the opening 312 (see FIG.4B). That is, even if the gate 330 is move upwardly and seals theopening 312, the sealing material 334 is separated from the surface 320of the gate valve seat 310 by the protective film 340, because theprotective film 340 is sandwiched between the sealing material 334 andthe surface 320 of the gate valve seat 310.

FIG. 5 is a schematic view of a wafer table of a lithography chamber inaccordance with some embodiments of the present disclosure. It is notedthat the lithography chamber 400 discussed in FIG. 5 is similar to thelithography chamber 271 discussed in FIG. 2.

The lithography chamber 400 includes a wafer table 405 having a tablebody 410 (e.g., stage frame). At least one wafer stage 415 is movablydisposed on to the table body 410, and therefore the table body 410 mayinclude a flat, level upper surface over which the wafer stage 415 canmove. It is noted that, the wafer stage 415 here can be similar to thewafer stages 272, 273 discussed in FIG. 2. In some embodiments, thewafer stage 415 may be coupled to the table body 410 via ananti-friction device (not shown). For example, the anti-friction devicemay include anti-friction bearings such as air bearings, fluid bearings,roller bearings or the like.

The wafer table 405 also includes a first sliding member 420 and asecond sliding member 430. In some embodiments, the second slidingmember 430 has a first portion 430A extending along the upper surface ofthe table body 410, and a second portion 430B on a sidewall of the tablebody 410. In some embodiments, the second portion 430B of the secondsliding member 430 is coupled to a slot 412 on the sidewall 411 of thetable body 410, such that the second sliding member 430 can be movablealong the sidewall 411 of the table body 410 in a first direction (e.g.,the X direction).

The second sliding member 430 further includes a track 432 coupled tothe first portion 430A. The track 432 extends along the upper surface ofthe table body 410 and extends in a second direction (e.g., the Ydirection). In some embodiments, the first sliding member 420 is movablymounted on the track 432 of the second sliding member 430, such that thefirst sliding member 420 can be movable along the track 432 of thesecond sliding member 430 in the second direction (e.g., the Ydirection).

The first sliding member 420 is further coupled to the wafer stage 415.As a result, the wafer stage 415 is also coupled to the second slidingmember 430 through the first sliding member 420. Accordingly, with suchconfiguration, the wafer stage 415 is movable over the upper surface ofthe table body 410 along a plane (e.g., X-Y plane) constructed by thefirst direction (e.g., the X direction) and the second direction (e.g.,the Y direction). For example, the wafer stage 415 can move along thefirst direction (e.g., the X direction) when the second sliding member430 is actuated to move along the slot 412 on the sidewall 411 of thetable body 410, and can move along the second direction (e.g., the Ydirection) when the first sliding member 420 is actuated to move alongthe track 432 of the second sliding member 430.

The wafer table 405 further includes a plurality of cables 440A, 440B,440C, and 440D with utilities. For example, each of the cables 440A,440B, 440C, and 440D may include a plurality of pipes which supplypressure dry air or vacuum air to the wafer stage 415, pipes whichsupply and recover a liquid for cooling the driving units (not shown)inside the wafer stage 415, and electric wires which transmit signalsand feed currents from a power source (not shown) and a controller (notshown) to the wafer stage 415. In some embodiments, first sides of thecables 440A and 440B are connected to the wafer stage 415, and secondsides of the cables 440A and 440B may be connected to a gas source, aliquid source, a power source, and/or a controller. Further, first sidesof the cables 440C and 440D are connected to the second sliding member430, and second sides of the cables 440C and 440D may be connected to agas source, a liquid source, a power source, and/or a controller. Insome other embodiments, the second sides of the cables 440A and 440B maybe connected to the second sliding member 430, and are connected to thefirst sides of the cables 440C and 440D through the second slidingmember 430. In some embodiments, the cables 440A and 440B aresubstantially parallel to each other and extend along the seconddirection (e.g., the Y direction), and the cables 440C and 440D aresubstantially parallel to each other and extend along the firstdirection (e.g., the X direction).

In some embodiments, at least one bracket 460 is configured to fix thecables 440A and 440B together, such that the cable 440A may be movablealong with the cables 440B. Similarly, at least one bracket 465 isconfigured to fix the cables 440C and 440D together, such that the cable440C may be movable along with the cables 440D. In some embodiments, thebrackets 460 and 465 are also configured to fix the pipes and/or wiresof each of the cables 440B, 440B, 440C and 440D, such that the pipesand/or wires of each of the cables 440B, 440B, 440C and 440D may bearranged neatly and in a desired order.

FIG. 6A is a schematic view of a wafer table a lithography chamber inaccordance with some embodiments of the present disclosure. FIG. 6B is aschematic view of a leaf spring of a wafer table of a lithographychamber in accordance with some embodiments of the present disclosure.FIGS. 6C and 6D are schematic views of a stopper of a wafer table of alithography chamber in accordance with some embodiments of the presentdisclosure. It is noted that FIG. 6A is a detailed view of the cables440A and 440B in the wafer table 405 as discussed in FIG. 5, and thusrelevant details will not be repeated for simplicity.

In FIG. 6A, a first bracket 510 fixes the cables 440A and 440B together,and a second bracket 520 fixes the cables 440A and 440B together. Withrespect to the first bracket 510, the first bracket 510 at leastincludes wider portions 512 and narrower portions 514 alternatelyarranged along the first direction (e.g., the X direction). For example,the width of each wider portion 512 is greater than the width of eachnarrower portion 514 along the second direction (e.g., the Y direction).In some embodiments, each of the wider portions 512 includes a throughhole for accommodating the cables 440A and 440B. In some embodiments,the narrower portions 514 are configured on opposite sides of each widerportion 512. At least one of the narrower portions 514 is between twowider portions 512, and thus this narrower portion 514 can also bereferred to as connecting portion between the two wider portions 512. Insome embodiments, the first bracket 510 and the second bracket 520 havesubstantially the same configuration, and thus relevant details will notbe repeated for simplicity.

A plurality of leaf springs 530 are fixed on the first bracket 510 andthe second bracket 520. In some embodiments, the leaf springs 530 arefixed on the first bracket 510 and the second bracket 520 by screws 535.Each leaf spring 530 is connected to a narrower portion of the firstbracket 510 and a corresponding narrower portion of the second bracket520. In some embodiments, each leaf spring 530 is a thin metal sheet,and has sufficient flexibility. In some embodiments, the leaf springs530 and the first and second brackets 510, 520 may be made of the sameor similar metal such as steel, stainless steel, or the like.

Frames 540 are disposed below the cables 440A and 440B and extendingalong the second direction (e.g., the Y direction). Referring to FIGS. 5and 6A, the frames 540 may horizontally extend to a position below thetable body 410 of the wafer table 405 and may be fixed to the table body410. In some embodiments, the frames 540 may be made of metal, such assteel, stainless steel, or the like. In some embodiments, the frames540, the leaf springs 530, and the first and second brackets 510, 520may be made of the same or similar material.

Stoppers 550 are disposed on the frames 540. In some embodiments, eachstopper 550 is fixed on a respective frame 540. Each stopper 550horizontally extends along the second direction (e.g., the Y direction).As discussed above with respect to FIG. 5, the wafer stage 415 ismovable along the upper surface of the table body 410, when the waferstage 415 is moved in a direction toward an edge of the table body 410(e.g., in the −Y direction of FIG. 5 toward the sidewall 411 of thetable body 410), the wafer stage 415 may push the cables 440A and 440Bin such direction, which will lead the first bracket 510 as well as theleaf springs 530 moving downwardly toward the frames 540. The stoppers550 over the frames 540 are configured to “stop” the leaf springs 530 tolimit the motion of the first bracket 510 and the leaf spring 530. Insome embodiments, the stoppers 550 and the leaf springs 530 are made ofdifferent material. For example, the leaf springs 530 made to made ofmetal, while the stoppers 550 may be made of polymer, such aspolyetheretherketone (PEEK).

In some embodiments, each of the stoppers 550 includes a first portion550A, a second portion 550B, and a third portion 550C. In someembodiments, the first portion 550A is connected to the second portion550B, and a slot 550S is between the second portion 550B and the thirdportion 550C. In some embodiments, the first portion 550A is narrowerthan the second portion 550B and the third portion 550C along the firstdirection (e.g., the X direction). This is beneficial because thenarrower first portion 550A would insert into the space between twoscrews 535 when the first bracket 510 is moved downwardly toward thestopper 550.

Protective films 560 are disposed on the leaf springs 530, andprotective films 570 are disposed on the stoppers 550. In someembodiments, each protective film 560 is disposed on a surface of theleaf spring 530 confronting a corresponding stopper 550. Similarly, eachprotective film 570 is disposed on a surface of the stopper 550confronting a corresponding leaf spring 530.

In FIG. 6B, the protective film 560 covers a portion of the surface ofthe leaf springs 530, while leaving portions on opposite sides of theleaf spring 530 exposed. In greater details, the portions of the leafspring 530 that are fixed by the screws 535 are not covered by theprotective film 560.

The protective film 560 has a length L1 and a width W1. In someembodiments, the length L1 is in a range from about 125 mm to about 130mm, such as 128 mm. In some embodiments, the width W1 is in a range fromabout 17 mm to about 21 mm, such as 19 mm. If the length L1 and thewidth W1 are too small, the protective film 560 may not have sufficientarea to cover the leaf spring 530. If the length L1 and the width W1 aretoo large, this may cause material waste and does not significantlyimprove the performance.

In FIG. 6C, the protective film 570 includes a first portion 570A, asecond portion 570B, and a third portion 570C, in which the firstportion 570A, the second portion 570B, and the third portion 570C aredisposed on the first portion 550A, the second portion 550B, and a thirdportion 550C of the stopper, respectively. That is, the slot 550S of thestopper 550 is free from coverage of the protective film 570.

The first portion 570A has a length LA and a width WA. In someembodiments, the length LA is in a range from about 8 mm to about 12 mm,such as 10 mm. In some embodiments, the width WA is in a range fromabout 3 mm to about 4 mm, such as 3.5 mm. The second portion 570B has alength LB and a width WB. In some embodiments, the length LB is in arange from about 118 mm to about 122 mm, such as 120 mm. In someembodiments, the width WB is in a range from about 14.5 mm to about 18.5mm, such as 16.5 mm. The third portion 570C has a length LC and a widthWC. In some embodiments, the length LC is in a range from about 58 mm toabout 62 mm, such as 60 mm. In some embodiments, the width WC is in arange from about 14.5 mm to about 18.5 mm, such as 16.5 mm. If thelengths LA, LB, LC and the widths WA, WB, WC are too small, theprotective film 570 may not have sufficient area to cover the stopper550. If the lengths LA, LB, LC and the widths WA, WB, WC are too large,the protective film 570 are too large, this may cause material waste anddoes not significantly improve the performance. In some embodiments, thefirst portion 570A is narrower than the second portion 570B and thethird portion 570C, and the second portion 570B have substantially thesame width as the third portion 570C.

In FIG. 6D, the protective film 570 may further includes a fourthportion 570D that covers the slot 550S of the stopper 550. That is, anentirety of the top surface of the stopper 550 is covered by theprotective film.

In some embodiments, the protective films 560 and 570 may be adhesivefilms, which is detachable from the surfaces of the leaf springs 530 andthe stoppers 550, respectively, and may be made of a material that isdifferent from the materials of the leaf springs 530 and the stoppers550. In some embodiments, the protective films 560 and 570 may include amaterial having friction coefficient less than 0.3, and having a tensilestrength (at break point) greater than 48 Mpa in vacuum. In someembodiments, the protective films 560 and 570 may be ultra highmolecular weight polyethylene (UHMWPE) tape. In some other embodiments,the protective films 560 and 570 may be silicon pressure sensitiveadhesive (PSA). In some embodiments, the protective films 560 and 570may satisfy a request in a Total Organic Carbon (TOC) test of outgassinglimit for refractories is zero (or negligible small) detected undertemperatures about 40° C. and about 100° C., this ensure that theprotective films 560 and 570 would not be decomposed under the selectedtemperatures, and would not contaminate other structures in thelithography chamber 400.

FIGS. 7A and 7B are side views of a wafer table of a lithography chamberin accordance with some embodiments of the present disclosure. Ingreater details, FIGS. 7A and 7B illustrate the structural relationshipsbetween the leaf spring 530 and the stopper 550 under differentconditions.

Referring to FIGS. 5 and 7A, FIG. 7A illustrates a first condition wherethe wafer stage 415 is in a first position away from an edge (e.g., theedge where the sidewall 411 locates) of the table body 410. For example,to reach the first position, the wafer stage 415 may be moved toward the+Y direction by moving the first sliding member 420 toward the +Ydirection along the track 432 of the second sliding member 430.Accordingly, the cable 440A (or cable 440B) is pulled inwardly, suchthat the first bracket 510 and the second bracket 520 may be raisedtogether with the cable 440A. As a result, the first bracket 510 and thesecond bracket 520 are spaced from the stopper 550, and the leaf spring530 is not in contact with the stopper 550. In greater detail, theprotective film 560 on the leaf spring 530 is separated from theprotective film 570 on the stopper 550 under the first condition.

Referring to FIGS. 5 and 7B, FIG. 7B illustrates a second conditionwhere the wafer stage 415 is in a second position close to the edge(e.g., the edge where the sidewall 411 locates) of the table body 410.For example, to reach the second position, the wafer stage 415 may bemoved, from the first position discussed in FIG. 7A, toward the −Ydirection by moving the first sliding member 420 toward the −Y directionalong the track 432 of the second sliding member 430. Accordingly, thecable 440A (or cable 440B) is pushed outwardly, such that the firstbracket 510 and the second bracket 520 may be lowered together with thecable 440A. As a result, the first bracket 510 and the second bracket520 are close the stopper 550, and the leaf spring 530 is in contactwith the stopper 550. In greater detail, the protective film 560 on theleaf spring 530 is in contact with the protective film 570 on thestopper 550 under the second condition. In some embodiments, the secondbracket 520 may be inserted to the slot 550S of the stopper 550. Asmentioned above, because the first portion 550A of the stopper 550 has anarrower width, the screws 535 on the first bracket 510 may bypass thefirst portion 550A of the stopper 550 and would not directly hit thefirst portion 550A of the stopper 550.

In some embodiments, because the protective films 560 and 570 aredisposed on the leaf spring 530 and the stopper 550, the leaf spring 530would not be in direct contact with the stopper 550 under the secondcondition of FIG. 7B. With this configuration, particles generated inthe chamber may be reduced by preventing direct rub or collision betweenleaf spring 530 and stopper 550. Accordingly, the wafer stage cleaningperiod can be extended. Further, because the particles are reduced, thewafer fall on particle count (which is determined by a wafer fall onparticle monitor) may be reduced.

In some embodiments, one of the protective films 560 and 570 may beomitted. For example, if the protective film 560 is omitted and theprotective film 570 is present, the leaf spring 530 would be in directcontact with the protective film 570 under the second condition of FIG.7B. On the other hand, if the protective film 570 is omitted and theprotective film 560 is present, the stopper 550 would be in directcontact with the protective film 560 under the second condition of FIG.7B.

FIG. 8 is a schematic view of a wafer table a lithography chamber inaccordance with some embodiments of the present disclosure. It is notedthat FIG. 8 is a detailed view of the cables 440C and 440D in the wafertable 405 as discussed in FIG. 5, and thus relevant details will not berepeated for simplicity.

In FIG. 8, a plurality of brackets 610 fixes the cables 440C and 440Dtogether. Similar to the first bracket 510 and the second bracket 520discussed in FIG. 6A, each of the brackets 610 may include widerportions and narrower portions alternately arranged. Different from thefirst bracket 510 and the second bracket 520 discussed in FIG. 6A,roller structures 630 are disposed on opposite sides of each of thebrackets 610. In greater detail, each roller structure 630 includes abody 632 and two wheels 634 disposed on opposite sides of the body 632.

The wafer table 405 further includes rail guides 640, in which two railguides 640 are disposed on opposite sides of each bracket 610. In someembodiment, each of the roller structures 630 is movable along a surfaceof a corresponding rail guide 640, in which the rail guides 640 arecapable of limiting the motion of the respective roller structures 630as well as the brackets 610. In some embodiments, the rail guides 640may include a curved shape. In some embodiments, the rail guides 640 maybe made of metal, such as steel, stainless steel, or the like.

The wafer table 405 further includes stopping plates 645 disposed overthe rail guides 640. In some embodiments, the stopping plates 645extends along the first direction (e.g., the X direction) and is coupledto ends of the rail guides 640. In some embodiments, the stopping plates645 may be a thin metal sheet, and has sufficient flexibility. In someembodiments, the stopping plates 645 may be made of metal such as steel,stainless steel, or the like aluminum. In some other embodiments, thestopping plates 645 may be made of polymer, such as polyetheretherketone(PEEK).

Protective films 660 are disposed on surfaces of the rail guides 640confronting the corresponding roller structures 630. In someembodiments, surfaces of the rail guides 640 distal to the correspondingroller structures 630 are free from coverage of the protective films660. In some other embodiments, the surfaces of the rail guides 640distal to the corresponding roller structures 630 may also be covered byprotective films.

Protective films 670 are disposed on surfaces of the body 632 of theroller structures 630 distal to the corresponding rail guides 640. Insome embodiments, each protective film 670 covers a middle portion ofthe body 632 of the corresponding roller structure 630, while oppositesides of the body 632 that are connected to the wheels 634 are notcovered by the protective film 670. In some embodiments, an entirety ofsurfaces of the body 632 of the roller structures 630 confronting thecorresponding rail guides 640 are free from coverage of the protectivefilms 670.

In some embodiments, the protective films 660 and 670 may be adhesivefilms, which is detachable from the surfaces of the rail guides 640 andthe roller structures 630, respectively, and may be made of a materialthat is different from the materials of the rail guides 640 and theroller structures 630. In some embodiments, the protective films 660 and670 may include a material having friction coefficient less than 0.3,and having a tensile strength (at break point) greater than 48 Mpa invacuum. In some embodiments, the protective films 660 and 670 may beultra high molecular weight polyethylene (UHMWPE) tape. In some otherembodiments, the protective films 660 and 670 may be silicon pressuresensitive adhesive (PSA). In some embodiments, the protective films 660and 670 may satisfy a request in a Total Organic Carbon (TOC) test ofoutgassing limit for refractories is zero (or negligible small) detectedunder temperatures about 40° C. and about 100° C., this ensure that theprotective films 660 and 670 would not be decomposed under the selectedtemperatures, and would not contaminate other structures in thelithography chamber 400.

FIGS. 9A and 9B are side views of wafer table of a lithography chamberin accordance with some embodiments of the present disclosure. Ingreater details, FIGS. 9A and 9B illustrate the structural relationshipsbetween the roller structures 630 and the rail guides 640 underdifferent conditions.

Referring to FIGS. 5 and 9A, FIG. 9A illustrates a first condition wherethe wafer stage 415 is in a first position. For example, to reach thefirst position, the wafer stage 415 may be moved toward the −X directionby moving the second sliding member 430 toward the −X direction alongthe slot 412 of the table body 410. Accordingly, the cable 440C (orcable 440D) is pulled upwardly, such that the bracket 610 and the rollerstructures 630 may be raised together with the cable 440C. Under thefirst condition, the roller structures 630 are moved upwardly along thesurface of the rail guide 640, and may be stopped at the top portion ofthe rail guide 640.

Referring to FIGS. 5 and 9B, FIG. 9B illustrates a second conditionwhere the wafer stage 415 is in a second position. For example, to reachthe second position, the wafer stage 415 may be moved toward the +Xdirection by moving the second sliding member 430 toward the +Xdirection along the slot 412 of the table body 410. Accordingly, thecable 440C (or cable 440D) is pushed downwardly, such that the bracket610 and the roller structures 630 may be raised together with the cable440C. Under the second condition, the roller structures 630 are moveddownwardly along the surface of the rail guide 640, and may be stoppedat the top portion of the rail guide 640.

The roller structures 630 may move up and down along the surface of therail guide 640. Because the protective film 660 is disposed on thesurface of the rail guide 640. The roller structures 630 may be incontact with the protective film 660 during the motion. With thisconfiguration, particles generated in the chamber may be reduced bypreventing direct rub or collision between roller structure 630 and therail guide 640. Accordingly, the wafer stage cleaning period can beextended. Further, because the particles are reduced, the wafer fall onparticle count (which is determined by a wafer fall on particle monitor)may be reduced.

FIG. 10 illustrates a method M1 of forming a semiconductor device inaccordance with some embodiments of the present disclosure. Although themethod M1 is illustrated and/or described as a series of acts or events,it will be appreciated that the method is not limited to the illustratedordering or acts. Thus, in some embodiments, the acts may be carried outin different orders than illustrated, and/or may be carried outconcurrently. Further, in some embodiments, the illustrated acts orevents may be subdivided into multiple acts or events, which may becarried out at separate times or concurrently with other acts orsub-acts. In some embodiments, some illustrated acts or events may beomitted, and other un-illustrated acts or events may be included.

At step S101, a wafer is transferred into a lithography chamber. Forexample, as discussed in FIG. 2, a wafer 250 may be moved from the waferhandler 260, through the load locks 264, 264 and the wafer exchangechamber 266, to the lithography chamber 271. In some embodiments, whenthe wafer 250 is moved from one space (e.g., a chamber) to another space(e.g., a chamber), the wafer 250 may pass through a corresponding gatevalve assembly (e.g., the gate valve assemblies 262, 263, 267, 268, and270) between the two spaces (e.g., two chambers).

Reference is also made to FIGS. 4A and 4B. Generally, before the wafer250 passes through the gate valve assembly 262, the gate valve assembly262 is “CLOSE” where the gate 330 presses against the protective film340 on the gate valve seat 310 to seal the opening 312 of the gate valveassembly. However, when the wafer 250 is about to pass through the gatevalve assembly 262, the gate valve assembly 262 may be “OPEN” to allowthe wafer 250 to pass through. As shown in FIG. 4A, the gate 330 ismoved downwardly away from the protective film 340 on the gate valveseat 310 to reveal the opening 312 of the gate valve seat 310.

At step S102, a wafer stage is moved to a first position to receive thewafer. At step S103, the wafer stage is moved to a second position wherethe wafer undergoes a lithography process. In some embodiments, afterthe wafer 250 is received by the wafer stage, the gate valve assembly262 may be “CLOSE” again, in which the gate 330 is moved upwardly topress against the protective film 340 on the gate valve seat 310 to sealthe opening 312 of the gate valve assembly (see FIGS. 4A and 4B).

From steps S102 to S103, the wafer stage may be moved over an uppersurface of a table body of a wafer table. As discussed in FIG. 5, thewafer stage 415 can be moved along a first direction (e.g., the Xdirection) and a second direction (e.g., the Y direction) by moving thesecond sliding member 430 and the first sliding member 420,respectively.

As discussed in FIGS. 7A and 7B, when the wafer stage 415 is moved backand forth along the second direction (e.g., the Y direction), theprotective films 560 and 570 may touch each other and then separate fromeach other alternately. Details have been discussed in FIGS. 7A and 7B,and thus relevant descriptions will not be repeated for simplicity.

As discussed in FIGS. 9A and 9B, when the wafer stage 415 is moved backand forth along the first direction (e.g., the X direction), the rollerstructure 630 may move up and down along the protective film 660 on therail guide 640. Details have been discussed in FIGS. 9A and 9B, and thusrelevant descriptions will not be repeated for simplicity.

At step S104, the lithography process is performed to the wafer. FIG. 1illustrates an example of the lithography process corresponding to actin step S101.

FIG. 11 illustrates a method M2 of forming a semiconductor device inaccordance with some embodiments of the present disclosure. Although themethod M2 is illustrated and/or described as a series of acts or events,it will be appreciated that the method is not limited to the illustratedordering or acts. Thus, in some embodiments, the acts may be carried outin different orders than illustrated, and/or may be carried outconcurrently. Further, in some embodiments, the illustrated acts orevents may be subdivided into multiple acts or events, which may becarried out at separate times or concurrently with other acts orsub-acts. In some embodiments, some illustrated acts or events may beomitted, and other un-illustrated acts or events may be included.

At step S201, a wafer is transferred into a lithography chamber. At stepS202, a lithography process is performed to the wafer. At step S203, thewafer is transferred out of the lithography chamber.

At step S204, whether a surface condition of a protective film in thewafer table is acceptable is determined. In some embodiments, theprotective film can be the protective film 340 discussed in FIGS. 3 to4B, can be the protective films 560 and 570 discussed in FIGS. 6A to 7B,and can also be the protective films 660 and 670 discussed in FIGS. 8 to9B. It is noted that the protective films 340, 560, 570, 660, and 670 ofthe embodiments may be made of the same material.

In some embodiments, the user can determine whether a contamination onthe surface of the protective film exceeds a threshold value. In someembodiments, the threshold value can include a number of particlesfalling on the surface of the protective film. In some otherembodiments, the threshold value can include a ratio of thecontamination area on the surface of the protective films to the wholearea of the surface of the protective film. In some other embodiments,the threshold value can include a number of scratches on the surface ofthe protective film.

If the surface condition of at least one of the protective films in thewafer table does not exceed the threshold value (e.g., the condition isacceptable), the method M2 then returns back to steps S201 and continuesproceeding operations Steps S202 through S203.

However, if the surface condition of the protective film in the wafertable exceeds the threshold value (e.g., the condition is unacceptable),the method M2 proceeds to step S205 where the protective film isreplaced with a new protective film. In some embodiments, replacing theprotective film with the new protective film can be done manually.

If the protective film is the protective film 340 discussed in FIGS. 4Aand 4B, the protective film 340 may be peeled off from the surface ofthe gate valve seat 310, and then a new protective film 340 may beattached to the surface of the gate valve seat 310. If the protectivefilm is the protective film 560 discussed in FIGS. 6A to 7B, theprotective film 560 may be peeled off from the surface of the leafspring 530, and then a new protective film 560 may be attached to thesurface of the leaf spring 530. If the protective film is the protectivefilm 570 discussed in FIGS. 6A to 7B, the protective film 570 may bepeeled off from the surface of the stopper 550, and then a newprotective film 570 may be attached to the surface of the stopper 550.If the protective film is the protective film 660 discussed in FIGS. 8to 9B, the protective film 660 may be peeled off from the surface of therail guide 640, and then a new protective film 660 may be attached tothe surface of the rail guide 640. If the protective film is theprotective film 670 discussed in FIGS. 8 to 9B, the protective film 670may be peeled off from the surface of the roller structure 630, and thena new protective film 670 may be attached to the surface of the rollerstructure 630.

According to the aforementioned embodiments, it can be seen that thepresent disclosure offers advantages in fabricating semiconductordevices. It is understood, however, that other embodiments may offeradditional advantages, and not all advantages are necessarily disclosedherein, and that no particular advantage is required for allembodiments. One advantage is that protective films are used to coversurfaces of several structures in a lithography chamber, and the surfaceof the structures can be protected during performing a lithographyprocess. With this configuration, particles generated in the chamber maybe reduced by preventing direct rub or collision between structure andstructure. Accordingly, the wafer stage cleaning period can be extendedby improving 50% wafer path cleaning (PM) available time (AVL). On theother hand, because the particles are reduced, the wafer fall onparticle count (which is determined by a wafer fall on particle monitor)may be reduced to about 0.6 ea to about 0.7 ea. Another advantage isthat, the protective film may be cheap and replaceable, it is easy to beapplied in a wide area in the lithography chamber, and can lower thecost of the cleaning process. Yet another advantage is that, theparticle generated rate on the protective film is low, which will alsoextend the cleaning period of the lithography chamber.

According to some embodiments of the disclosure, a method includestransferring a wafer over a wafer stage on a wafer table. The wafertable includes a table body, a wafer stage, a first sliding member, asecond sliding member, a first cable, a first bracket and a secondbracket, and a stopper. The wafer stage is moveably disposed over thetable body. The first sliding member is coupled to the wafer stage. Thesecond sliding member is coupled to an edge of the table body, thesecond sliding member being movable along a first direction, in whichthe first sliding member is coupled to a track of the second slidingmember, the first sliding member being movable along a second directionvertical to the first direction. The first cable is coupled to the waferstage and extending along the second direction. The first bracket andthe second bracket fix the first cable, the first and second bracket areconnected by a leaf spring. The stopper is disposed below the firstcable. The method includes moving the wafer stage toward the edge of thetable body, such that the wafer stage pushes the first cable outwardly,such that the leaf spring is moved toward a first protective film on asurface of the stopper facing the leaf spring. In some embodiments,moving the wafer stage toward the edge of the table body is performedsuch that the first protective film is in direct contact with a secondprotective film on a surface of the leaf spring facing the stopper. Insome embodiments, moving the wafer stage toward the edge of the tablebody is performed such that the second bracket is moved downwardly intoa slot of the stopper, and the slot of the stopper is free from coverageof the first protective film. In some embodiments, moving the waferstage toward the edge of the table body is performed such that thesecond bracket is moved downwardly into a slot of the stopper, and asurface of the slot of the stopper is covered by the first protectivefilm. In some embodiments, the wafer table further includes a secondcable, a third bracket, and a rail guide. The second cable is coupled tothe second sliding member and extending along the first direction. Thethird bracket fixesthe second cable, the third bracket being coupled toa roller structure, in which the roller structure comprises a body and awheel coupled to the body. The roller structure is moveable along asurface of the rail guide. The method includes moving the wafer stagealong the first direction, such that the roller structure is moved alonga second protective film on a surface of the rail guide. In someembodiments, a third protective film is disposed on the body of theroller structure. In some embodiments, the method further includesdetermining whether a surface condition of the first protective film isacceptable; and replacing the first protective film with a new firstprotective film in response to the determination determines that thesurface condition is unacceptable. In some embodiments, a surface of theleaf spring facing the stopper is free from coverage of a protectivelayer. In some embodiments, the first protective film is made of ultrahigh molecular weight polyethylene (UHMWPE) tape and silicon pressuresensitive adhesive (PSA).

According to some embodiments of the disclosure, a method includestransferring a wafer into a first chamber of a load lock, the firstchamber being coupled to a gate valve assembly having a gate valve sealand a gate pressing against a protective film on a surface of the gatevalve seal; moving the gate downwardly away from the protective film onthe surface of the gate valve seal to reveal an opening of the gatevalve seal; transferring the wafer from the first chamber, through theopening of the gate valve seal, to a second chamber; and performing asemiconductor process to the wafer in the second chamber. In someembodiments, the method further includes after performing thesemiconductor process to the wafer, determining whether a surfacecondition of the protective film is acceptable; and replacing theprotective film with a new protective film in response to thedetermination determines that the surface condition is unacceptable. Insome embodiments, replacing the protective film with the new protectivefilm includes peeling off the protective film from the surface of thegate valve seal; and attaching the new protective film on the surface ofthe gate valve seal. In some embodiments, the method further includesafter transferring the wafer from the first chamber to the secondchamber and prior to performing the semiconductor process, moving thegate upwardly to press a sealing material of the gate against theprotective film on the surface of the gate valve seal again. In someembodiments, an entirety of the surface of the gate valve seal isseparated from the sealing material of the gate by the protective filmwhen the sealing material of the gate is pressed against the protectivefilm. In some embodiments, the protective film is made of ultra highmolecular weight polyethylene (UHMWPE) tape and silicon pressuresensitive adhesive (PSA).

According to some embodiments of the disclosure, a lithography systemincludes a table body, a wafer stage, a first sliding member, a secondsliding member, a first cable, a first bracket, a rail guide, and afirst protective film. The wafer stage is moveably disposed over thetable body. The first sliding member is coupled to the wafer stage. Thesecond sliding member is coupled to an edge of the table body, thesecond sliding member being movable along a first direction, in whichthe first sliding member is coupled to a track of the second slidingmember, the first sliding member being movable along a second directionvertical to the first direction. The first cable is coupled to thesecond sliding member and extending along the first direction. The firstbracket fixes the first cable, the first bracket being coupled to aroller structure, in which the roller structure includes a body and awheel coupled to the body. The rail guide confines a movement of thewheel of the roller structure. The first protective film is adhered to asurface of the rail guide, in which the roller structure is moveablealong the first protective film on the surface of the rail guide. Insome embodiments, the body of the roller structure has a surface distalto the surface of the rail guide, and the surface of the body of theroller structure is covered by a second first protective film. In someembodiments, the lithography system further includes a second cable, asecond bracket and a third bracket, and a stopper. The second cable iscoupled to the wafer stage and extending along the second direction. Thesecond bracket and the third bracket fix the first cable, the second andthird brackets are connected by a leaf spring. The stopper is disposedbelow the first cable, in which the stopper has a surface facing theleaf spring, and the surface of the stopper is covered by a secondprotective film. In some embodiments, the second protective film has afirst portion, a second portion, and a third portion, the first portionbeing connected to the second portion, and the third portion isseparated from the second portion by a slot of the stopper, in which thefirst portion is narrower than the second portion and the third portion.In some embodiments, the lithography system further includes a gatevalve assembly having a gate valve seal, a gate, and a second protectivelayer. The gate is detachably coupled to the gate valve seal, in whichthe gate includes a sealing material presses against a surface of thegate valve seal. The second protective layer covers the surface of thegate valve seal.

The foregoing outlines features of several embodiments so that thoseskilled in the art may better understand the aspects of the presentdisclosure. Those skilled in the art should appreciate that they mayreadily use the present disclosure as a basis for designing or modifyingother processes and structures for carrying out the same purposes and/orachieving the same advantages of the embodiments introduced herein.Those skilled in the art should also realize that such equivalentconstructions do not depart from the spirit and scope of the presentdisclosure, and that they may make various changes, substitutions, andalterations herein without departing from the spirit and scope of thepresent disclosure.

What is claimed is:
 1. A method, comprising: transferring a wafer over awafer stage on a wafer table, the wafer table comprising: a table body,the wafer stage being moveably disposed over the table body; a firstsliding member coupled to the wafer stage; a second sliding membercoupled to an edge of the table body, the second sliding member beingmovable along a first direction, wherein the first sliding member iscoupled to a track of the second sliding member, the first slidingmember being movable along a second direction vertical to the firstdirection; a first cable coupled to the wafer stage and extending alongthe second direction; a first bracket and a second bracket fixing thefirst cable, the first and second bracket are connected by a leafspring; and a stopper disposed below the first cable; and moving thewafer stage toward the edge of the table body, such that the wafer stagepushes the first cable outwardly, such that the leaf spring is movedtoward a first protective film on a surface of the stopper facing theleaf spring.
 2. The method of claim 1, wherein moving the wafer stagetoward the edge of the table body is performed such that the firstprotective film is in direct contact with a second protective film on asurface of the leaf spring facing the stopper.
 3. The method of claim 1,wherein moving the wafer stage toward the edge of the table body isperformed such that the second bracket is moved downwardly into a slotof the stopper, and the slot of the stopper is free from coverage of thefirst protective film.
 4. The method of claim 1, wherein moving thewafer stage toward the edge of the table body is performed such that thesecond bracket is moved downwardly into a slot of the stopper, and asurface of the slot of the stopper is covered by the first protectivefilm.
 5. The method of claim 1, wherein: the wafer table furthercomprises: a second cable coupled to the second sliding member andextending along the first direction; a third bracket fixing the secondcable, the third bracket being coupled to a roller structure, whereinthe roller structure comprises a body and a wheel coupled to the body;and a rail guide, wherein the roller structure is moveable along asurface of the rail guide; and the method further comprises moving thewafer stage along the first direction, such that the roller structure ismoved along a second protective film on a surface of the rail guide. 6.The method of claim 5, wherein a third protective film is disposed onthe body of the roller structure.
 7. The method of claim 1, furthercomprising: determining whether a surface condition of the firstprotective film is acceptable; and replacing the first protective filmwith a new first protective film in response to the determinationdetermines that the surface condition is unacceptable.
 8. The method ofclaim 1, wherein a surface of the leaf spring facing the stopper is freefrom coverage of a protective layer.
 9. The method of claim 1, whereinthe first protective film is made of ultra high molecular weightpolyethylene (UHMWPE) tape and silicon pressure sensitive adhesive(PSA).
 10. A method, comprising: transferring a wafer into a firstchamber of a load lock, the first chamber being coupled to a gate valveassembly having a gate valve seal and a gate pressing against aprotective film on a surface of the gate valve seal; moving the gatedownwardly away from the protective film on the surface of the gatevalve seal to reveal an opening of the gate valve seal; transferring thewafer from the first chamber, through the opening of the gate valveseal, to a second chamber; and performing a semiconductor process to thewafer in the second chamber.
 11. The method of claim 10, furthercomprising: after performing the semiconductor process to the wafer,determining whether a surface condition of the protective film isacceptable; and replacing the protective film with a new protective filmin response to the determination determines that the surface conditionis unacceptable.
 12. The method of claim 11, wherein replacing theprotective film with the new protective film comprises: peeling off theprotective film from the surface of the gate valve seal; and attachingthe new protective film on the surface of the gate valve seal.
 13. Themethod of claim 10, further comprising: after transferring the waferfrom the first chamber to the second chamber and prior to performing thesemiconductor process, moving the gate upwardly to press a sealingmaterial of the gate against the protective film on the surface of thegate valve seal again.
 14. The method of claim 13, wherein an entiretyof the surface of the gate valve seal is separated from the sealingmaterial of the gate by the protective film when the sealing material ofthe gate is pressed against the protective film.
 15. The method of claim10, wherein the protective film is made of ultra high molecular weightpolyethylene (UHMWPE) tape and silicon pressure sensitive adhesive(PSA).
 16. A lithography system, comprising: a table body; a wafer stagemoveably disposed over the table body; a first sliding member coupled tothe wafer stage; a second sliding member coupled to an edge of the tablebody, the second sliding member being movable along a first direction,wherein the first sliding member is coupled to a track of the secondsliding member, the first sliding member being movable along a seconddirection vertical to the first direction; a first cable coupled to thesecond sliding member and extending along the first direction; a firstbracket fixing the first cable, the first bracket being coupled to aroller structure, wherein the roller structure comprises a body and awheel coupled to the body; a rail guide confining a movement of thewheel of the roller structure; and a first protective film adhered to asurface of the rail guide, wherein the roller structure is moveablealong the first protective film on the surface of the rail guide. 17.The lithography system of claim 16, wherein the body of the rollerstructure has a surface distal to the surface of the rail guide, and thesurface of the body of the roller structure is covered by a second firstprotective film.
 18. The lithography system of claim 16, furthercomprising: a second cable coupled to the wafer stage and extendingalong the second direction; a second bracket and a third bracket fixingthe first cable, the second and third brackets are connected by a leafspring; and a stopper disposed below the first cable, wherein thestopper has a surface facing the leaf spring, and the surface of thestopper is covered by a second protective film.
 19. The lithographysystem of claim 18, wherein the second protective film has a firstportion, a second portion, and a third portion, the first portion beingconnected to the second portion, and the third portion is separated fromthe second portion by a slot of the stopper, wherein the first portionis narrower than the second portion and the third portion.
 20. Thelithography system of claim 16, further comprising a gate valveassembly, the gate valve assembly comprises: a gate valve seal; a gatedetachably coupled to the gate valve seal, wherein the gate comprises asealing material presses against a surface of the gate valve seal; and asecond protective layer covering the surface of the gate valve seal.